This FAQ is the
creation of Frank Monroe, who has agreed to let this FAQ be hosted here at Ars Technica
and at other locations.

I created this FAQ because, after reading
literally thousands of posts, I still see the same requests for basic instructions over
and over in each Newsgroup and forum. There are many web sites with similar
information, but many people either can't find these sites or they don't have web
access. Since I have never seen a FAQ like this posted in any of the Newsgroups I
read, I took it upon myself to offer this small contribution to novice overclockers
everywhere. I don't claim to have all the answers and I can't guarantee that
everyone will be able to overclock their Celeron, but after reading this FAQ you should be
well on your way to a successful experience.

Overclocking is not recommended by any
manufacture (especially Intel) and will void your warranty. I do not advise anyone
to follow these instructions unless they are willing to assume all associated risks.
I have consolidated in this document information that I've learned while overclocking my
own system or that I have read about the experiences of others. Overclocking can
damage your system. Working inside your power supply or wiring 110 volt fans can
cause serious personal injury if done by the inexperienced or without the proper
precautions. If you're unsure or in doubt about any of these procedures, seek
professional advice. I am providing this document for informational purposes only.

If any one out there in Net-land has
suggestions, comments or contributions for this FAQ, feel free to contact me. Frank
Monroe email: monroef001@hawaii.rr.com

So, you want to overclock a Celeron?

You've read a few post, maybe visited a few
web sites. Everyone is reporting their success and claiming fantastic speeds from a
lowly 266 or 300 MHz CPU. You're excited at the prospect of a high performance CPU
for, essentially, small change and you want to get in on the action. The speed of a
P2-400 or -450 for $90 or $150 sounds too good to be true. But wait, they're talking
about S-codes, multiplier locking, Pin B21, CAS-2, and other esoteric terms. Names
like Deschutes, Klamath and Mendocino are bandied about while you wonder what these words
have to do with computers. Now you're confused. How hard is this going to
be? Is it worth it? Do you need to be an Electrical Engineer to
overclock a Celeron? In a word, no. With the right hardware and a little luck,
it should be a snap.

Why is the Celeron so overclockable?

As you may know, a given chip design is
used for CPU's of many different speeds. The P2 and Celeron designs are named after
Western US rivers: Deschutes, Klamath and Mendocino. More on this later.

In theory, a CPU is tested first at it's
maximum speed. The ones that pass the testing process at this speed are marked as
such and sold as top-of-the-line CPU's. Those that fail at the fastest speed are
tested at successively lower and lower speeds until they run reliably. These slower
cores are then marked with the speed at which they passed the testing process and sold as
slower processors. At least, that's the theory. No one really knows how Intel
decides which cores get marked for a given speed. Several other factors, such as
customer demand and production quality, affect how many processors of each speed are
produced.

A CPU of any given speed can usually be
made to run somewhat faster if one is willing to play around with the motherboard
settings. This is the overclocker's bread and butter. Now, through a convenient turn
of events, Intel has produced a CPU with an unusually high capacity for overclocking.

Intel has long controlled the high-end CPU
market while its competitors, Cyrix and AMD were gaining market share in the low- and
mid-price range because of the popularity of lower priced PC's. Intel finally
realized what was happening and wanted to recover the low ground while also keeping the
high end market (can you say "total market domination"?). When Intel
designed the CPU core for their newest line of processors, the P2, they changed the way
the CPU was mounted. All P2's are mounted on a circuit board, called an SECC (Single
Edge Contact Cartridge), that plugs into a special, patented CPU slot (Slot 1) similar to
a PCI slot. [Intel calls the Celeron packaging a SEPP (Single Edge Processor
Package) but it's still compatible with the Slot 1 connector, go figure.] AMD
and Cyrix do not have a Slot 1 CPU, so if you want high-end speed, you need to buy an
Intel processor. Thus the high-end market is preserved for Intel. Now,
Intel needed a cheap Slot 1 CPU to corner the low-cost PC market.

Enter the Celeron line. To reduce
production costs, Intel left out the expensive Level 2 cache. Also, to eliminate
design costs, the original Celerons (C266 and C300) used the same CPU core as the new
350-450 MHz P2's (code name Deschutes). [Remember, design costs account for a huge
percentage of the total cost of a CPU. Once in production, it costs exactly the same
to manufacture a core destined for use as a 266 MHz processor as it does to use that same
core in a 450 MHz processor.] Many media pundits immediately dubbed the Celeron a
backward-stepping piece of crap because of the lack of the L2 cache. Later, perhaps
due to the poor reviews from hardware critics, Intel released the Celeron 300A and 333
with 128 Kb of built-in cache. Again, they used basically the same core design with some
modifications to incorporate the on-die cache. The C300A and the C333 modified
Deschutes core carries the code name Mendocino. Since Celerons use a
Slot 1 motherboard, you can't upgrade to one of Cyrix's or AMD's fast new CPU's later,
when prices come down. They don't have Slot 1 CPU's and Intel has the patent.
Now Intel has again regained a foothold in the below-$1000 PC market and insured that the
upgrade dollars also come home to Papa Intel too.

Here's where it gets interesting. The
fastest P2 CPU's (350 to 450) require a relatively new type of Slot 1 motherboard with the
BX chipset. The BX motherboard runs at a bus speed of 100 MHz. They can also
run at 66 MHz bus which allows them to accept slower P2 CPU's (233, 266, 300 and 333) and
Celerons. The Celerons are supposed to be used on the earlier EX and LX generation of Slot
1 motherboards which run at 66 MHz only. Since the Celerons have the exact same core
as the new architecture P2 CPU's, there's nothing to stop you from setting the bus
to 100 MHz and running a Celeron at 400 or 450 MHz.

People started buying BX motherboards and
Celerons and overclocking the hell out of them by setting the bus speed to 100 MHz. A chip
meant to run at 266 running at 400 MHz and more was unheard of previously. It's all
because Intel is trying to capture the low-cost CPU market without the R & D costs of
a new chip. It's really a marketing stroke of genius when you think about it.
Produce one type of CPU. Take the best ones, add 512 kb of fast, expensive cache and
sell it as the top-of-the-line CPU for $700+. Take the rejects, leave off the
expensive L2 cache and sell them as cheap Celerons. Except they're too smart for
their own britches. The production yield of 450 MHz cores is too good and the
"rejects" are too few and far between. Because they want to flood the
market with $100 CPU's, they have to mark them as 266 to 333 MHz Celerons and sell them
cheap anyway. It doesn't cost them any more since both chips came off the same
production line. Because the P2-450 market is relatively small compared to the low-
and mid priced market, the demand is greater for Celerons.